A marker pen, fineliner, marking pen, felt-tip marker, felt-tip pen, flow, marker or texta (in Australia) or sketch pen (in India), is a pen which has its own ink-source, and a tip made of porous, pressed fibers such as felt.[1] A permanent marker consists of a container (glass, aluminum or plastic) and a core of an absorbent material. This filling serves as a carrier for the ink. The upper part of the marker contains the nib that was made in earlier time of a hard felt material, and a cap to prevent the marker from drying out. Until the early 1990s the most common solvents that were used for the ink were toluene and xylene. These two substances are both harmful and characterized by a very strong smell. Today, the ink is usually made on the basis of alcohols (e.g. 1-propanol, 1-butanol, diacetone alcohol and cresols).

Lee Newman patented a felt-tipped marking pen in 1910.[2] In 1926 Benjamin Paskach patented a "fountain paintbrush"[3] as he called it which consisted of a sponge-tipped handle containing various paint colors. Markers of this sort began to be popularized with the sale of Sidney Rosenthal's Magic Marker (1953) which consisted of a glass tube of ink with a felt wick. By 1958 use of felt-tipped markers was commonplace for a variety of applications such as lettering, labeling, and creating posters.[4] The year 1962 brought the development of the modern fiber-tipped pen (in contrast to the marker, which generally has a thicker point) by Yukio Horie of the Tokyo Stationery Company (which later became Pentel).

Permanent markers are porous pens that can write on surfaces such as glass, plastic, wood, metal, and stone. The ink is generally resistant to rubbing and water, and can last for many years. Depending on the surface and the marker used, however, the marks can often be removed with either vigorous scrubbing or chemicals such as acetone.

A non-permanent marker (also called a whiteboard marker or dry-erase marker) uses an erasable ink, made to be used on a slick, non-porous writing surface, for temporary writing with overhead projectors, whiteboards, and the like. They may also be used by children, making marks that are easy to clean. The erasable ink does not contain the toxic chemical compounds xylene and/or toluene as have been used in permanent markers.

Wet erase markers are another version that are used on overhead projectors, signboards, whiteboards, and other non-porous surfaces.

Special "security" markers, with fluorescent but otherwise invisible inks, are used for marking valuables in case of burglary. The owner of a stolen, but recovered item can be determined by using ultraviolet light to make the writing visible.

A porous point pen contains a point that is made of some porous material such as felt or ceramic. Draftsman's pens usually have a ceramic tip since this wears well and does not broaden when pressure is applied while writing.

The use of the terms "marker" and "felt-tipped pen" varies significantly among different parts of the world. This is because most English dialects contain words for particular types of marker, often generic brand names, but there are no such terms in widespread international use.

In India, felt-tip pens are referred to as "sketch pens" because they are mainly used for sketching purposes whereas the permanent felt-tip markers are referred to as just "markers". In Malaysia and Singapore, marker pens are simply called markers. In the Philippines, a marker is commonly referred to as a "Pentel pen", regardless of brand. In Indonesia, a marker pen is referred to as "Spidol". In South Korea and Japan, marker pens are referred to as "sign pens," "name pens," or "felt pens." In Japan, permanent pens are also referred to as "Magic" (from a famous pen brand name).

In Australia, the term "marker" usually refers only to large-tip markers, and the terms "felt-tip" and "felt pen" usually refer only to fine-tip markers. Markers in Australia are often generically called "texta", after a brand name of a type of permanent marker. Some variation in naming convention occurs between the states, for example in Queensland the brand name "nikko" has been commonly adopted.

The common German term for felt pen is Filzstift or "Filzschreiber" (colloquial "Filzer") or "Fasermaler". These are often used by children for sketching purposes, and should not be toxic. A highlighter is called Textmarker or "Leuchtstift" (the verb "leuchten" means to shine or to glow / the noun "Stift" means pen). Permanent markers are usually referred to as Edding after the leading brand for markers.

The generic term used for most felt-tip pens in Romania is "carioca" (pl. "carioci"), after the brand name of the first commercialised felt tips in Romania during the communist period. In recent times, the English word "marker" has been adopted (spelled as in English but with the plural "markere") and is used especially when referring to the permanent and highlighter variety of felt-tip pens.

In the United States, the word "marker" is used as well as "magic marker", the latter being a genericized trademark. The word "sharpie" is also now used as a genericized trademark.

In Canada and the US, "Magic Marker" is sometimes used to refer to "reveal markers" for "magic picture books" where the colors of a picture are revealed by a colorless marker. Sharpie is a popular brand of permanent markers used for labeling. Markers are also sometimes referred to as felt-pens or felts in some parts of Canada.